Impulse television system



March 2, 1937.

A. M L. NICOLSON IMPULSE I TELEVISION, SYSTEM Original Filed June 25,196 0 5 Sheets-Sheet 1 H MM INVENTOR AAsxanaer M lean Mao/son.

BYQLf W ATTORNEY oi'iginal F ile d June 25, 1930 5 Sheets-Sheet- 2INVENTOR Akxander M Lean Nico/son.

QM/KM ATTORNEY 5 Sheets-Sheet 3 ATTORNEY INVENTOR March 2, 1937. A. M L.NICOLSON IMPULSE TELEVISION SYSTEM Original Filed June 25, 1950Alexander M Lean N/co/son.

w W @W x W Y T. V- L P om mw mm March 2, 1937. A. M L. NICOLSON IMPULSETELEVISION SYSTEM Original Filed June 25, 1930 5 Sheets-Sheet 4 INVENTORflkxander M Lwm N/CO/sfln.

ATTORNEY March 2, 1937. A. M L. NICOLSON IMPULSE TELEVISION SYSTEMOriginal Filed June 25, 1930 5 Sheets-Sheet 5 vr k INVENTOR Alexander M-Lean Nico/son.

Patented Mar. 2, i 1937 UNITED STATES IMPULSE TELEVISION SYSTEMAlexander McLean Nicolson, New York, N. Y

assignor .to Communication Patents, Inc.. New York, N. Y., a corporationof Delaware Application June 25, 1930; Serial No. itascz Renewed July29, 1936 13 Claims.

This inventidn relates to the transmission of intelligence in the formof images, and particularly to the transmission thereof on electriccurrent impulsel.

An object or this invention is to transmit electrical'vibrationscorresponding to the light and shade oi an object or picture thereof andthe reproduction of the light and shade intensities at a distance. I

Another object of the invention is to transmit television electricalvibrations by the use of an electrical thermionic commutator whichserves as a scanning and transmitting generator.

A further object of the invention is to obtain 15 perfectsynchronization between the scanning medium and the receiving medium.

A still further object of the invention is the transmission oftelevision currents and accompanying sound currents over the sameapparatus.

The transmission of electrical currents obtained through the scanning ofan object with light or otherwise, the currents being generated by aphotoelectric cell receiving the varying light intensities, necessitatesthe use of a broad irequency transmission channel. This transmission isusually accomplished on carrier frequencies within a definite range andhas, therefore, definite limitations from a capacity standpoint. in thisinvention the transmission oi the frequencies generated in thephotoelectric cell is accomplished on positive half cycle impulses, thetransmission irequency being, in fact, thescanning speed.

To obtain such a high scanning, speed, a thermionic commutator oi thetype disclosed in my copehding application Ser. No. 460,806, tiled Juneid, 1930, is employed. This commutator has no mechanical parts whatever,and produces current impulses atsubstantially any speed desired up tothe speed of light. These current impulses are used to produce asearching light ray while accompanying voice or sound may be transmittedon any one of the impulses not being used for scanning. Other signals ofa monitoring nature the actuating impulses, although two commuta-.

tors operating at the proper speed difference will 5 reduce the numberof tube elements to the arithmetical sum of the electrodes instead ofthe square thereof.

The details of the invention will be more fully understood from theaccompanying drawings in which: Figures la and 1b are diagrammaticsketches of transmitting and'receivin'g apparatus, respec-" tively,.of atelevision system in accordance with tion.

In Fig. la a transmitting screen 5 of the type to be describedhereinafter, scans an object 6. 25

Light projected through a pinhole 8 of a camera 9 is reflected upon aphotoelectric cell iii. The currents generated in the cell it areimpressed upon an amplifier ii connected to transmission apparatus ii. Agenerator-translator it sup- 30 plies the screen a with current impulsesto produce the scanning light over conductors contained in cable it. Amicrophone i'i detects any sound produced by the object or objects beingscanned, the electrical sound currents being im- 35 pressed upon anamplifieriB connected to the transmitter it. The generator-translator isshown connected to the transmitting apparatus it, for the transmissionof synchronizing impulses and the sound modulated impulses. The 40output of transmitter i2 is impressed upon antenna system hi) or wireconductors ii. The transmitter may comprise either amplifiers whichampliiy only the generator-translator impulses after modulation by thephotoelectric cell currents, or may comprise a carrier frequencymodulator. A modulator-oscillator system is not required when theimpulses are generated at a sufilciently high frequency.

Referring to Fig. 1b', receiving antenna 25 or wire conductors 28 feedreceiving apparatus 21 which is.oi.' the type depending upon thetransmitter i2. An amplifier 28 amplifies the-received signals beforeimpression on a generator-translator 29. The output of thegenerator-translator 29 is connected to a receiver screen 88 by a cable8| containing the screen electrode conductors.

Also connected to the generator-translator is a lustrate one terminal ofa television system which may be used either for transmitting orreceiving,

or for two-way transmission.

In Fig. 2 a portion 48 of a scanning or receiving screen is illustratedby a co-ordinate set of conductors, a certain proportion of which areconnected up to energizing transformers to show the operation of thesystem. This screen may be of the, type disclosed in Fig. 6, or any typeof screen which has a plurality of spark gaps or light producing pointswhich, by energization from a voltage source in a certain order, willproduce a searching beam of light. 'In the present drawing electrodes4|,. 42 and 49 comprise a portion of one set of coordinates, anclelectrodes 44, 48 and 48 comprise a portion of the other set ofco-ordinates. These electrodes may be of metallic conducting materialsseparated sufllclently to allow a certain voltage to produce a sparktherebetween, and may be closed within an evacuated envelope or a gasfilled tube,-although this is not necessary, since the essential objectof the screen is to produce a visible light.

The above numbered electrodes produce in the present screen nineintersecting points. .These points have voltage supplied through linetransformers 49 to 81, inclusive. To produce a spark at the intersectionof the electrodes 4| and 44, a voltage impulse is impressed upontransformer 49 connected between the electrodes. To produce a sparkbetween electrodes 42 and 44, a voltage impulse is impressed upontransformer 88 which is connected between these two electrodes, and soon for all the nine intersections. The voltage impulses are impressedupon the transformers in some definite serial order from an impulsegenerator shown in Fig. 3. Only a portion of this generator is shown butthe. missing sections are inserted at the broken lines identical withthose illustrated, and need not be shown in detail. The portion of thegenerator shown is composed of vacuum tubes 81 to 8|, inclusive. Thesetubes are interconnected .by delay circuits 88 to 88, inclusive, oneelement of each being a'variable condenser for controlling the rate ofgeneration of the impulses, and consequently the scanning speed of thelight produced at the intersections of the electrodes.

Such an impulse generator is disclosed in detail in my copending U. 8.application referred to above.

The filaments of these tubes are shown supplied by a filament battery18, while the anodes thereof are supplied from the high potential sourceII. The grids are all biased from a'common grid potential source 12,which has in series therewith a resistance 18. This resistance, shuntedby two-way rectifiers 89 and 99 in series with the secondariesoftransformers 88 and 98, is a synchronizing element for the commutatorcircuit. shunting the grid-biasing battery is a key 14 employed for thepurpose of changing the starting impulse, and which may be used forframing the picture when the circuit is functioning as'a receiver. It isalso useful for starting the original impulse which, after it is onceinitia'ted, is propagated through the tubes.

Each tube has aninput and output circuit coupled through respectivetransformers. For instance, tube 89 has an output transformer I8 feedingtwo conductors I1 connected to transformer 49, the voltage transmittedtherethrough producing a spark or discharge at the intersection ofelectrodes 4| and 44. Likewise vacuum tube 8| through output transformerI 9 and over conductors 88 produces a voltage impulse in transformer 55,which initiates a spark between electrodes 4| and 48. The otherelectrode intersections are supplied in the same manner from tubesconnected in the generator between tubes 88 and 59.

The output transformers of the various tubes have three windings, thethird winding of which is connected in series with similar windings ofthe other transformer, as shown by -the series circuit 82. This circuitincludes the primary of transformer 83 of the synchronizer, and theprimary of a transformer 84 in the input of a modulator circuit 88. Eachimpulse produced, therefore, is impressed upon the input of themodulator system 88 comprising a'vacuum tube 81 and a second inputtransformer 88, as well as the rectifier 89 through transformer 83. Theoutput of the modulator is connected through an output transformer 98 toa hybrid or separating transformer 9| well known in two-way telephonepractice, which permits transmission of the out- .put to an antennasystem 92 or wire conductors 98 chosen by means of a switch 94. Abalancing network 88 is employed to balance the hybrid coil and preventthe output currents from reentering the system.

Returning to the generator system, the tubes have input transformerswhich are all connected in parallel and to'the, incoming line at thehybrid coil 9|. Any input impressedupon a tube when operative will betransmitted to the respective intersection of the electrodes in themanner above discussed. The incoming voltages are maintained at a levelwhich is insufllcient to operate the tubes. In parallel with theincoming line is the primary of transformer 98, which impresses theincoming impulses upon the rectiher 88 which is polled reversely withrespect to the rectifier 89.

It is obvious that all the tubes shown in the commutator circuit are notconnected to the electrodes of the screen. These tubes, namely 51 and88, are shown connected to a loud speaker I88 and a microphone pick-updevice I8l through amplifiers I82 and I89, respectively. The output oftube 81 is connected to the loud speaker through output transformer I88,while the input of tube 58 is connected through input transformer II8 tothe microphone. In Fig. 2

is also shown a photo-electric cell device I88.

connected to an amplifier I88 by means of conductors I81 and transformer88 to the modulator system 88.

As a transmitter, the system operates as follows: The key 14 is closedshorting the grid potential '12, and permitting current impulses tothrough the pinhole 8 of camera 8 in Fig. 1a, and

onto an object. Reflected light from the ob- Ject will fall uponphotoelectric cell I06, will be amplified by amplifier I and impressedupon the input of tube 01 of the modulator 06. The

' two tubes 51 and 50 of the generator are, preferably, placed in thecircuit after each complete cycle of the sparks over the scanningscreen, the rapidity of propagation causing no appreciable break betweencycles in the scanning of the object. impulses from all the tubes,however, will be generated in the series circuit 82 and impressed on theinput of modulator tube 81 through the transformer 84. At substantiallythe same instant that the photoelectric cell currents arrive at thetransformer 88 in the modulator, the generator impulse will arrive atthe transformer 84 in the same circuit. After passage of the impulsecurrents,'which are nonoverlapping half cycles, through the trans former04, they are alternating current of high frequency which is thefrequency of the rate of propagation of the impulse through theelectrical impulse generator. This high frequency wave will constitutethe carrier current necessary for transmission of the photocell currentswhich modulate it. These modulated picture currents will be transmittedto the'transformer 90 and to the antenna or wire conductors fortransmission to a receiver. Each impulse, therefore, not only producesthe scanning light, but the carrier cycle for transmitting thephotoelectric cell currents produced by this light.

If the objects being scanned produce sound, such sound will be detectedby microphone i0i, amplified in amplifier I03 and transmitted to theinput of tube 58 through input transformer H0. when the rotating impulseof the generator has reached tube 58, this tube will be-,

come operative through removal of the heavy grid bias obtained frombattery '12, and will transmit the sound during the time the im- Lationthereof as a receiver being as follows:

pulse has the bias removed. This impulse will be transmitted to theseries circuit 82 and into *the modulator system 08 through transformer84. Since this tube produces no light on the screen, there will be nophotoelectric currents to interfere with the modulation of this cycle inthe modulator 86, and the sound currents modulated in tube 58 will,therefore, be transmitted between photoelectric cell currentmodulations. Since the impulse occurs at the tube 58 at such a highrapidity, sufficient portions of the sound signal will be transmitted toconstitute intelligent reception thereof at the receiver. A moredetailed explanation of this operation will be foundin' my copendingapplication referred to above. a

The impulses produced as described, are transmitted, and may be receivedon a system-identical with the one shown in Figs. 2 and 3, the oper- Theimpulses are received over'antenna system 92 or wire conductors 98 andtransmitted through hybrid coil ill in the direction shown by the arrowarriving at the input circuits of all-the tubes simultaneously throughrespective input transformers. The same screen may be used as a receiverwithout the pinhole camera shown in Fig. la. As a receiving screen, anobserver will see only a solidly lighted screen of one light intensitywhen no received currents are being transmitted to the screen. As thecurrents are received from the transmitter in the input circuits of the.tubes, the impulse transmitted to the screen is varied in intensity.That is, it may be of lesser brilliance or greater brilliance inaccordance with the modulation thereof by the photoelectric cellcurrents at the transmitter. For instance, an impulse may be received inthe tube I50 such that it will reduce the amplitude of the rotatingimpulse, and therefore, produce a lower voltage at the transformer 40.The discharge between electrodes ll and 44 is now of less intensity thanthat produced by the tube with the normal or local impulse. The reverseaction occurs if the incoming impulse increases the local generatingimpulse. The reception, therefore, of varying strength signals orimpulses at the various tubes at definite times, will produce a changingintensity of the light produced at the intersections and reproduce onthe receiving screen the corresponding light and shade intensities ofthe object being scanned at the transmitter.

The transmitting and receiving impulses are kept in step and in the sameorder by the automatic synchronizer 13. The locally generated impulsesare impressed through the transformer 03 on the rectifier 09, andproduce a direct current voltage drop across resistance 83 which willalter the grid biasing voltage in a certain direction. The incomingimpulses are impressed upon the rectifier 09 through the transformer 08,and produce a biasing potential in the reverse direction with respect tothe impulses received through transformer 83. The amplitude of theseimpulses impressed on the rectiflers is adjusted so that when thesystemis at synchronism, that is, the generators at the receiver andtransmitter, are rotating at the same rate of speed, the impulsesreceived will exactly neutralize each other and there will be no changein grid bias on the local tubes. However, should one or the other of thegenerators tend to stray from synchronization, a differential voltagewill be obtained which, when rectified, will produce a bias, in theproper direction to speed up orslow down one or the other of thesystems. The speed of rotation is controlled by the length of time animpulse takes tov pass through a tube, and is dependent upon theamplitude of the impulse. By reducing the amplitude of the impulse ineach tube, a more rapid propagation may be obtained by a circulatingimpulse. Of course, any appreciable speed change is effected by thetuning elements of the delay circuits 63 to 06, inclusive, which may bemounted so adjustments may be made as a single unit.

It will be noted that a third function of the generated impulses has nowbeen described. That is, the impulses provide the scanning or imagelight, the carrier frequency for transmitting. the photocell currents,and the grid biasing voltage to control the speed of generation of theimpulses which maintains synchronism between any two generators.

The sound which has been transmitting on the definiteimpulsecorresponding with tube 58 will be received in the input circuitof tube- 51, as these connections are reversed at the transmitter andtransmitted through the output transformer. I00 to the loud speaker I00,the loud speaker being placed in an appropriate position with respectto-the screen, to reproduce the sound with the picture. The transmittingand receiving sound circuits are maintained separately by separate timechannels by the generators operating in synchronism.

To accomplish two-way transmission it is only necessary to provide afunction changing ele- 4 will serve.

ment which will change the function of the system from a transmitter toa receiver and vice versa at a super-audible rate such as not tointerfere with the continuity of either function. A system of this typeis disclosed in my copending application Ser. No. 397,826, filed October7, 1929. I

In Fig. 4 a screen H5 has ten co-ordinate electrodes in eitherdirection, which provides 100 intersections or light points. In theconnections of the system of Figs. 2 and 3 such a screen requires 100transformers which may increase the expense of such a system beyondpractical limits, and prohibit its manufacture. To reduce this number oftransformers, however, the system of Fig. In this system two commutatorswhich operate at different rates of speed are provided. For instance, acommutator H6 rotates as rapidly as a commutator H1. Each of thesecommutators are generators of the same type as shown in Fig. 3, exceptthey are connected in series and at different speeds. The segments ofeach generator shown represents the vacuum tube which has been connectedup in accordance with the circuit of Fig. 3, the only element shownbeing the three winding output transformers. The serial connection ofthe third winding of these transformers is connected to both generatorsin serieshaving output terminals H8 which connect to a modulator system86 and a synchronizer 13, such as shown in Fig. 3. This system operateson a combined voltage basis, that is, it requires the voltage generatedby any one of the tubes of generator I I1 combined with the voltagegenerated by any one of the tubes H6 to produce a light or spark wherean electrode I20 and an electrode I2I intersect as point I22. To producea spark at this intersection, a voltage must be generated by tube I24 inseries with tube I25 of generator I I1. That is, the circuit is fromelectrode I20 through the secondary of the output transformer of thetube I24 through the common conductor I26, the secondary of outputtransformer of tube I25 to electrode I2I. To produce a spark at theother intersections of the electrode I20, the generator H1 makes onecomplete cycle before the impulse passes through tube I24 of .thegenerator H6. In this manner light discharges are produced alongelectrode I20. As the impulse then changes from tube I24 to tube I28 forinstance, light will be produced at all intersections along electrodeI29, as an impulse rotates around the system I I1. In other words thesystem H1 is rotating ten times as fast as the system I I6.

Referring to 'Fig. 5, a chart is shown between time and amplitude of thegenerated impulses for this system. The generator H6 is generating avoltage shown by the three positive wave sections "a, b and 0, whilesuperimposed thereon are the smaller amplitude impulses produced by thegenerator H1. The amplitude of the impulses a, b and c are insufficientto produce a spark unless augmented by the impulses produced by thegenerator H1. By the use of this arrangement, therefore, the amount ofapparatus required is considerably smaller than that of the systems ofsources I36 in the form of incandescent lamps. These light sources maybe of any type, however, such as the co-ordinate electrodesabovedescribed or neon lamps. The tubes may be bent in variousdirections within the angle of refraction, to provide more space in therear of the screen to accommodate the light sources. 'These lamps areener.

gized from the output of a generator system parbe used in the twogenerator system of Fig. 4, each.

generator of which rotates at a speed commensurate with the number oflight sources employed.

Any other suitable light producing means may be employed in this system,which can be enertially represented by the block sections I31 to I41, I

gized from current impulses produced in the manner disclosed.Furthermore, the system is adaptable to other embodiments of atelevision system, without departing from the spirit of the invention,and is to be limited only by the scope of the appended claims.

What is claimed is:

1. A television transmission system comprising means for producingrapidly occurring current impulses, a coordinate electrode system, meansfor impressing said impulses on said system in a serial order, means forscanning an object with a plurality of light beams generated betweensaid electrodes by said impulses, means for transforming light from saidobject into said electrical currents, and means for mixing said impulseswith said last-mentioned currents.

2. A television transmission system comprising a screen havingcoordinate electrodes separated from one another in two planes, meansfor producing a plurality of current impulses, means for causing saidimpulses to flow between said electrodes at a plurality of differentpositions to produce a plurality of light rays in a serial order, meansfor transforming said light into electrical currents, and means. formixing said current im pulses with said last-mentioned currents.

3. In a television system, means for producing current impulses, a.plurality of distributed electrodes, said impulses and said electrodesproducing a searching ray of'light for said system in the form of aseries of electrical discharges, a photoelectric cell, and means fortransmitting on said impulses the photoelectric cell currents.

4. A television system comprising means for producing rapidly occurringcurrent impulses, means for impressing said impulses on a plurality ofcoordinate electrodes in a definite order to produce a plurality oflight beams spatially disposed, a photoelectric cell for receivingchanging light intensities 'caused by said current impulses, and meansfor combining said impulses and the currents generated by saidphotoelectric cell.

5. A television transmission system comprising a plurality ofdistributed electrodes, a transmitting impulse current generator' forproducing a plurality of light beams at mutually exclusive intervals andspatially disposed between said 'plurality of electrodes in a definiteorder, means for transformingsaid light into corresponding electricalcurrents, a similar impulse generator for illuminating a receivingscreen in synchronism with the light beams produced bysaid transmittinggenerator, means for combining said transaorasas formed electricalcurrents and the output current of said transmitting generator, meansfor transmitting said combined currents to said receiving.

said elements in a definite order at a rapid rate of speed, means fortransforming said light modulated by objects being scanned intoelectrical currents, means for transforming the sound produced 2 Vbysaid objects being scanned into electrical currents, and means forsuccessively combining said object modulated currents and saidaccompanying sound currents with the output currents of said generatorin a predetermined order.

8. A television system comprising a transmitting station and a receivingstation, means at said transmitting station for producing a scanning rayof light, said means including 'a tandem connected plurality of vacuumtubes generating cur- 30 rent impulses between electrodes, means fortransforming said light into electrical current,

impulses characterized by the light and shade densities of an object,means for combining said last mentioned currents with said generatedcur- 35 rent impulses. means at said receivingstation for producinglight in synchronism with the production of said scanning ray, saidmeans including a tandem connected plurality of vacuum tubes generatingcurrent impulses between similarly ar- 40 ranged electrodes, and meansfor transmitting said combination currents between said pluralitiesof'tubes to maintainsynchronism between said scanni g ray and saidreceiver light and to reproduce image of said object. f

45 9; Ina television transmission system in which current impulsescharacterized by the light and shade of an object are transmitted, aplurality of electrodes arranged to form a definite area, aphotoelectric cell, a plurality of electronic de- 50 vices for producingsaid currentimpulses at a definite rate of speed for impressionon' saidelectrodes to produce a spatially disposed series of light beasnameansformixing said impulses with the currents from said photoelectric cell,and

'55 means for employing said impulses to control the rated generation ofsaid impulses.

ments, a current impul'segenerator for energizing Y currents.

10. In a television system, a thermionic commutator producing rapidlyoccurring current impulses, means for impressing a majority of saidimpulses on a scanning screen for scanning an object, means fordetecting sound accompanying the objects being scanned, and means fortransmitting said sound on the impulses of said commutator not employedfor producing scanning i a t.

'11. In a television transmission system, a plurality of electrodesdisposed in parallel, a second plurality of electrodes disposed inparallel and normal to said first plurality of electrodes, a pluralityof vacuum tubes arranged in tandem to transmit therethrough a currentimpulse in serial order, means for connecting the output of each of saidvacuum tubes to electrodes 'at mutually ex-p elusive intersections, theoutput voltage from said tubes producing an electrical discharge betweensaid electrodes at said respective intersections. means for transforminga portion of the light from said discharges into electrical currents,and means for combining-said current impulses and said last mentionedcurrents for transmission to a receiving point.

12. In a television transmitting system, a plurality of'electrodesdisposed in parallel in one plane, a plurality of electrodes disposed inparallel normal to said first plurality of electrodes in a second planeequidistant from said first plane,-,

a. plurality of thermionic devices having their output circuitsconnected to said electrodes, said thermionic devices producing atrespective intersections between said pluralities of electrodesdischarges in a pre-arranged order, a modulating device, means forimpressing on said modulating device the output of all of saidthermionic devices,

means for transforming the light from-said electrical discharges intocorresponding electrical currents, and means for impressing upon saidmodulator said transformed electrical currents for transmission asmodulations of the output forming said light beams into correspondingelectrical currents in accordance with the light and shade densities ofsaid object, and combining the current impulses 'withlthe transformedelectrical Amman McLEAN moor-eon.

